Various methods are used to correct the speech of persons affected by stammering. One of such methods consists in applying to the hearing organ of the person through an audio signal transmission channel his own speech delayed in time (cf. "Primenenie apparata "Ekho" pri ustranenii zaikaniya", Leningrad, 1979, p.p. 8-9). When this method is employed, the speaking person hears the words pronounced by himself with a time delay in relation to the instants at which they were spoken. Such a method makes it possible to separate the time of reception of speech from the time of utterance and thus enables the person to better concentrate on the speech fragments pronounced by him and helps him to overcome stammering. The duration of the time delay can be adjusted so as to choose the amount of delay most suitable for a given person.
According to the known method, application of the person's speech to his hearing organ is carried out in the relatively wide frequency range from 0.4 to 3 kilohertz, which provides a fairly high intelligibility of the speech signal supplied to the hearing organ of the person, as well as the conveyance of the timbre and intonation (emotional colouring) of the speaking person's voice. Besides, in the course of the transmission of speech the audio signal transmission channel remaines switched on both during speech fragments and during the pauses therebetween.
Therefore, the known method provides a relatively good quality of transmission of the speech sounds, which, from the viewpoint of electroacoustics, is an asset. However, as the therapeutic practice has shown, such speech transmission is not optimal as far as the treatment of stammering is concerned. This is due to the fact that, with the known method, the hearing organ of the person is supplied, during transmission of his speech, with a large amount of superfluous information which is semantically iseless, i.e. not needed by the person to perceive the meaning of the words pronounced by him, and yet has distracting influence on the person. Such superfluous information is represented by the information on the timbre and emotional colouring of the speech, as well as by the environmental noise and the internal noise of the audio signal transmission channel when both kinds of noise are not drowned by the person's speech, i.e. during the pauses between the speech fragments pronounced by the person. The application of this superfluous information increases the emotional excitement of the person, distracts his attention and hinders speech perception, which makes it difficult for the person to overcome stammering so that the correction of speech becomes less effective.
The method described above is carried out with the aid of a device comprising an acoustical-electrical transducer, a delay unit and an electrical-acoustical transducer, all connected in series (cf. "Primenenie apparata "Ekho" pri ustranenii zaikaniya", Leningrad, 1979, p.p. 8-9). The acoustical-electrical transducer is a laringophone which is to be applied to the person's throat, the electrical-acoustical transducer being an earphone which is to be positioned at the person's ear, while the delay unit is a magnetic tape recorder having its recording head connected through an amplifier to the laringophone and its reproducing head connected through another amplifier to the earphone and adapted to be moved with respect to the recording head by means of a fine adjustment screw, which makes it possible to adjust the time delay of the speech signal.
During application of the person's speech to his hearing organ, this device provides continuous transmission of a relatively wide frequency spectrum through the circuit including the electrical-acoustical transducer, the delay unit and the electrical-acoustical transducer and therefore has the same disadvantages as the known method of correcting speech described above.